JPS6034708B2 - In-vehicle radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle-mounted radar device with an optimized detection area.

Current vehicle-mounted radars use a fixed beam system in which the beam direction with respect to the antenna is constant, and therefore, when detecting a vehicle traveling in front, problems as shown in FIG. 1 occur.

Figure 1 a shows the state when driving straight, and b shows the state when driving on a curve. In these figures, A is the own vehicle (vehicle equipped with radar), B,
B', C are the vehicles traveling ahead, E is the cedar beam detection area, G
is the guardrail, R is the lane in which the vehicle is traveling, and R is the adjacent lane. In Figure 1a, vehicle A can detect vehicle C, which is ahead in the same lane R as vehicle A, using its on-board radar, but vehicles such as vehicle B', which cut in at a close distance, are outside the detection area. It cannot be detected because it enters the blind spot. If vehicle B' is traveling in the same direction as vehicle A, there is no need to detect it, but if it approaches the vehicle, it should be detected as soon as possible and the vehicle should be evacuated or braked. I need to go in. In addition, in Figure 1b, vehicle A should detect vehicle C in front of it in driving lane R, but if the lane is curved, fixed beam radar cannot detect this and instead does not detect it. Vehicle B and guardrail G in the adjacent lane R' are detected. There is no need to detect guardrails, roadside signs, or other signs as long as the steering wheel is operated correctly. It is not a system in which humans judge the displayed pattern, and it does not have the ability to recognize patterns, so it is impossible to determine whether it is a guardrail or a moving vehicle, and false alarms are inevitable. Therefore, a method has been proposed that uses a sensor other than radar, such as a centripetal accelerometer, to detect a curve when driving around a curve, and uses the signal to reduce the detection distance of the radar and reduce malfunctions. However, this is not a proactive method.

The present invention aims to improve the above points and provide a vehicle guidance radar device that can optimize the radar detection area (coverage) by combining beam direction change and line cut functions.

The in-vehicle radar device of the present invention includes a scanning antenna that horizontally scans the radiation direction of the cedar beam and forms an obstacle detection area of a certain angle in front of the vehicle in the traveling direction, and generates a signal indicating the vehicle's traveling direction. The traveling direction of the vehicle is determined from the sensor and the signal, and based on the results, the range of each radar beam is individually adjusted so that the detection area for the traveling direction is large and the other detection areas are small. The present invention is characterized in that it is equipped with a received signal processor that limits the amount of noise, and is entirely mounted on the vehicle.This will be described in detail below with reference to embodiments. FIG. 2 shows the switching state of the radar beam detection area according to the present invention.

Beams E, , E2, and E3 are emitted from the wheel A adjacent to the front thereof and spread in three directions, and these beams have a detection area of L, , -, and L by means of a beam cut. If these range cuts are made appropriately, Figure 2 a, b,
As shown in c, the detection area can be adjusted to suit the driving route. That is, Fig. 2 a shows the case of a left curve, and the range of the left radar beam E is set to the longest L, the range of the center radar beam E2 is set to the middle L2, and the range of the right radar beam E3 is set to the shortest. By setting it to L3, the radar beam detection range is tilted to the left as a whole according to the driving direction, so that areas other than the driving lane of own vehicle A are not detected, and the blind spot in the front and right direction is is decreasing. Figure b shows the case of a straight road.The center radar beam E2 is set to the longest L, and the radar beams E, IE3 on both left and right legs are set to the middle L2, and the detection area is set within the vehicle's driving lane. The blind spot is reduced by expanding left and right, and it is possible to quickly detect and warn a high-speed cutting-in vehicle B' at close range, as shown in FIG. 1a. Figure c shows the case of a right curve, with the radar beam E3 on the right being the longest L, the center radar beam E2 being the middle L, and the left radar beam E being the shortest L.
By setting it to 3, the detection area of the radar beam as a whole is tilted to the right, achieving the same effect as in the case of FIG. 2a. Any method can be used to set this range.

For example, the range cut is made in accordance with the rotation angle of the steering wheel, and when driving straight, the beam E. , E2, and E3 to predetermined ranges L, L, and L to obtain the state shown in Fig. 2b, and in the case of a left turn or right turn, set the pre-memorized ranges L, L, and L3 according to the bending angle. All you have to do is read them out and use them to range-cut beams E, E2, and E3. As a sensor other than the handle, a centripetal accelerometer or the like can be used. Wheel speed should also be taken into consideration when determining the range. The range cut that imposes restrictions on the detection distance differs depending on the radar system, but is performed as follows, for example.

That is, if the detection distance is R, then in the case of pulse radar R=K,・t...mIn the case of FM-CW radar, R=K2・fr...■ However,
K,, K2; proportionality constant t; time fr; range frequency is established.

Therefore, the range can be easily cut by using a time gate or filter to remove signals longer than a certain time or signals above a certain frequency. Beam E. ~E3
To create this, it is recommended to use a scanning antenna.

These can be roughly divided into mechanical scanning antennas shown in Figure 3,
There are two types of electrically scanned antennas shown in FIG. Further, as a mechanical scanning antenna, a method using a solenoid as shown in FIG. 3a, and a method using a cam and a motor as shown in FIG. 3b and c are conceivable. In these figures, D is a fixed beam antenna, F is a beam direction, P is a fulcrum, S,, S2 are solenoids, Cm is a power arm, M is a motor, 1 is an array axis of the array antenna, 1, 2,... , n is the antenna element, and d is the element spacing. In Fig. 3a, the fixed beam antenna D rotates clockwise and counterclockwise about the fulcrum P by passing current through the solenoids S, S2 in opposite phases to excite them, and the beam direction F is rotated left and right. oscillate. In the figure b, a cam Cm having the shape shown in the figure c is rotated by a motor M, and the fixed beam antenna D is moved to a fulcrum P by pushing up one end of the fixed beam antenna ○ through a cam receiver 〇' attached to one end of the fixed beam antenna ○. It rotates clockwise and counterclockwise around , and swings left and right in the beam direction F. To create the beams E, , E2, and E3 shown in Figure 2, the cam Cm has the largest diameter part Cm, the middle part Cm2, and the smallest diameter part Cm3.
When these portions Cm, , Cm2, and Cm3 come into contact with the cam receiver ○, the beams radiated from the antenna D become E, , E2, and E3. In the case of Fig. 2a, only the solenoid S, is excited and the beam E, solenoid S,
, S2 can be excited to create the beam E2, and only the solenoid S2 can be excited to create the beam E3. The number of time divisions of the beam is not limited to three, and it goes without saying that the more divisions there are, the more preferable the shape of the radar detection area will be.

In Fig. 4, element 1 of the array antenna is set as the phase center,
If the phase difference of other equally spaced elements 2, 3, . . . , n is sequentially 16, 26, 36, . The radiation characteristic E is expressed as {3' below, and the angle of beam direction F from the array antenna normal line is 8 m (direction of maximum radiation characteristic) {
4) It is shown in Eq.

E8=E, tens of E2ej, tens of E3ej2, . ．． Ten En
of ei(n-1). ．． ．．・'3'8m=Sin-1 Ryo.・・・． ...[4' However, E: the amplitude of the electric field strength of each element - dSina + 6 d; element spacing: 8; angle from the array normal: 6: inter-element phase difference: free space wavelength, that is, the inter-element phase difference of 6 By setting it to an arbitrary value, the beam can be directed in any direction.

However, this method requires the use of a large number of phase shifters that change the phase difference, which increases the cost.

To change the beam direction without using a phase shifter, it is recommended to use a slot antenna with a slot cut in the waveguide. The phase difference 6 in the slot array antenna is expressed by the formula {5}. 6 = Tame d-stroke.・・・． - Fence However, input g; waveguide internal wavelength d: slot spacing '8m from formula 5).

m = Shu (Crow house).・・・．・To change the beam direction, simply change the frequency or the length of the waveguide.

However, if you try to change the required range of 8 m in the beam direction using only the frequency, the frequency change will become extremely wide, so it is better to roughly match the length extension of the waveguide.
Shown below.

In FIG. 5a, a zigzag propagation path is formed by partition walls W3 and W4 that alternately protrude in a comb-like shape from side walls W, W2, and slots SL are provided at every pitch on one side wall W2. , Figure b shows a waveguide bent in a zigzag shape, and a slot SL similarly provided on the ~ side. This increases the length of the propagation path and eliminates the need to change the frequency so much. Figure 6 shows FM- as a vehicle combat radar.
An embodiment of the present invention using a CW radar is shown. In this figure, BC is a beam controller, MOD is a modulator, and OS is
C is an oscillator (transmitter) whose output is a directional coupler DC
is supplied to the transmitting antenna TA through. RA is a receiving antenna, and its output is added to the mixer MIX together with the branched output of the directional coupler DC, and guided to the signal processor ST via the amplifier AMm. K is a vehicle attitude detector.
To explain the operation of this device, first, the oscillator OSC sends a continuous wave FM modulated by the modulator MOD to the transmitting antenna T.
radiates from A.

When the aforementioned slot array antenna is used as the antenna TA, the beam controller BC performs frequency sweeping to change the direction of the beam radiated from the antenna TA to E, E2, E3,
Change sequentially as follows. If there is a target in front of the transmitting antenna, the transmitting beam from the transmitting antenna TA is delayed depending on the distance to the target and is received by the receiving antenna RA as a reflected wave, and one of the transmitting waves from the directional coupler DC. and mixer MIX. The mixer MIX produces a beat output of the frequency difference between the two inputs, which is applied to the signal processor ST where it is amplified by the amplifier AMP. In addition, as mentioned above, the vehicle attitude detector K detects the bending angle of the steering wheel, etc., and provides information regarding the direction of travel of the vehicle, i.e., going straight, turning left,
Information on the right turn is sent to the signal processor ST.

Information regarding the traveling direction from the detector K and a signal indicating the beam direction from the beam controller BC are input to the signal processor ST, and based on the output information from the detector K, the range cut level shown in FIG. 2 is input. Range cut is performed by setting L, ~L3 and using a time gate or filter for each beam direction based on the output signal of the beam controller BC to remove signals longer than a certain time or signals above a certain frequency. I do. The easiest way to switch the detection area shown in Fig. 2 is to set the ratio of ranges L, L2, and L3 in advance, for example, 1:0.7:0.5, and then use the signal from detector K to It is only necessary to judge whether to curve to the right, curve to the left, or go straight, and then change the range as shown in a to c in the same figure.

In this case, the degree of the curve, that is, the curvature, is not considered, so the configuration of the signal processor ST is simple. For example, the numerical values L = 6h, L2 = 42h, and L3 = 3h are stored in the memory, and these values are selectively input in response to the signal from the detector K, as shown in Fig. 2 a to c. This is because detection areas with different beam ranges may be formed for each direction. If there is an obstacle within the detection area, an alarm and/or commands Q for various actuators are output.

As explained in detail above, according to the present invention, by combining a range cut and a scanning antenna, the blind spot of the in-vehicle radar device is narrowed when driving on curves and when driving straight, improving detection performance. Defects such as erroneous detection by detecting unnecessary ranges during driving can be eliminated, and appropriate detection can be performed.

[Brief explanation of the drawing]

1A and 1B are explanatory diagrams of a conventional vehicle tracking radar device, FIGS. 2A to 2C are explanatory diagrams of the detection area of the radar device of the present invention, and 3
Figures a, b, and c are explanatory diagrams of scanning antennas, and Figure 6 shows an embodiment of the present invention applied to an FM-CW radar device. A, B, B', C... Traveling vehicle, D... Beam antenna, E, E, ~E3... Radar beam area, L~
L3... Range, R, R'... Driving lane, S, .
S2...Solenoid, Cm. ... power beam, SL...slot, BC... beam controller, TA, RA... antenna,
OSC...Oscillator, MOD...Modulator, MIX...
・Mixer, DC...Directional coupler, ST...Processor, AMP...Amplifier, K...Attitude detector, Q...
Command. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Scope of Claims] 1. A scanning antenna that scans the radiation direction of the radar beam in the horizontal direction and forms an obstacle detection area of a certain angle in front of the vehicle in the traveling direction, and generates a signal indicating the vehicle's traveling direction. The traveling direction of the vehicle is determined from the sensor and the signal, and based on the result, the detection area for the traveling direction is large;
and a reception signal processor that limits the detection area by individually adjusting the range of each radar beam so that the other detection areas are small, and the entire object detection device is mounted on the vehicle. in-vehicle radar equipment. 2. The vehicle-mounted radar device according to claim 1, wherein the scanning antenna comprises a fixed beam antenna and a drive mechanism that swings the antenna. 3. The in-vehicle radar device according to claim 1, wherein the scanning antenna is an array antenna consisting of a plurality of elements to which transmission signals having different phases are sequentially input. 4. The vehicle-mounted radar device according to claim 1, wherein the scanning antenna is a slot array antenna.